Call forwarding features, namely, Call Forwarding No Answer (CFNA), Call Forwarding Busy Line (CFBL), and Call Forwarding Default (CFD), are commonly available to wireless network subscribers. When invoked, these features permit calls for which a busy or no answer condition has been detected to be automatically transferred to a corresponding voice mail system. Such voice mail systems enable callers to leave voice messages for wireless subscribers when the subscriber has powered off his or her handset, is out of coverage, is engaged in another wireless call, or, for whatever reason, elects not to answer the incoming call. The routing to the voice mail systems in all of these conditions is controlled by the above call forwarding features. These feature forward all unanswered incoming calls to a single, fixed destination—a voice mail system.
A prior art wireless communication system is shown in FIG. 1 and designated generally by reference numeral 10. Wireless network 10 includes a Central Office Switch (COS) 12. COS 12 is provided in communication with the Public Switched Telephone Network (PSTN) 14 and one or more subscribers, each having at least one Customer Premises Equipment (CPE) device 16. COS 12 is further provided in communication with a Mobile Switching Center (MSC) 20 and an Intelligent Peripheral (IP) 22. MSC 20 is, in turn, provided in communication with IP 22, a Home Location Register (HLR) 24 and one or more Base Station Controllers (BSCs) 26. Each BSC 26 is provided in communication with one or more Base Stations (BSs) 28. Finally, each BS 28 is provided in communication with one or more mobile hand sets 30 each having an assigned calling number known as a Mobile Directory Number (MDN) or Mobile Identification Number (MIN). Each handset 30 also has a preassigned Electrical Serial Number (ESN).
In operation, a call to a mobile subscriber having handset 30, whether originated from a wireless network or a wire line network, is forwarded through the Public Switched Telephone Network (PSTN) 14 to COS 12. COS 12 performs a database look-up and identifies the Called Party DN as corresponding to a mobile subscriber. COS 12 then forwards the call to the subscriber's home MSC 20. MSC 20 will thereafter launch a query to HLR 24 requesting the location of handset 30, as well as call termination parameters. This request, termed a Location Request Message (LOCREQ), typically includes information such as calling party identification (the subscriber's DN or MIN) and redirecting party identification, the details of which are well known in the art and need not be discussed in further detail here. Thereafter, MSC 20 alerts handset 30 by generating a ringing signal.
In an ANSI-41 network, HLR 24 periodically receives update information regarding the location and call parameters for subscriber 30. This typically occurs wherever subscriber 30 “powers on” or enters a wireless serving area and initiates the registration process. Again, as those skilled in the art will recognize, handset 30 detects the presence of a Base Station (BS) 28 or Base Station Controller (BSC) 26. BS 28 or BSC 26, in turn, alerts the serving MSC, here MSC 20, that the handset 30 has begun registration. MSC 20 thereafter sends a Registration Notification Message (REGNOT) to HLR 24 requesting call termination parameters for handset 30. HLR 24 then sends a Registration Notification Response Message (regnot) to MSC 20. The REGNOT provides the above-referenced call termination parameters for subscriber 30 including whether the party has subscribed to any call forwarding features such as the above-referenced CFBL, CFNA or CFD. MSC 20 then stores this information for subsequent processing.
Single number services such as U S West One Number Service™ provide a subscribing party the ability to simultaneously receive a ringing signal from a calling party at a plurality of CPE devices. Although each CPE device has a different calling number or DN, a calling party need only dial a “single” calling number or primary number. Each of the subscriber's DNs for corresponding CPE devices are stored at HLR 24 and cross-referenced with the subscriber's primary number. For example, a subscriber may have a primary calling number of (303) 541-4000 and individual Directory Numbers of (303) 672-2985, (303) 672-2781, and (303) 672-2986 corresponding to the subscriber's office, home, and mobile telephones, respectively. A calling party, however, need only dial the primary number (303) 541-4000. Using the primary number, COS 12 will perform a database look-up and identify the call as directed to a party that has subscribed to one number service. COS will thereafter forward the call to Intelligent Peripheral (IP) 22. IP 22 will launch a query to HLR 24 requesting the specific DNs corresponding to the primary DN. HLR 24 will perform a suitable database look-up and provide this information to IP 22 along with the corresponding call termination parameters for each mobile handset 30. IP 22 will thereafter generate and bridge the calls to all of the subscriber's DNs. Calls to land line or “wired” telephones, such as telephone 16, are forwarded over the PSTN 14 to a serving switch, such as COS 12, and routed accordingly. Calls to mobile or “wireless” telephones, such as handset 30, are forwarded over the wireless network to a serving MSC, such as MSC 20.
Regardless, if a call to a wireless handset 30 originates from MSC 20 as a direct call, or from IP 22 as part of a one number service, MSC 20 will initiate a call forward feature if handset 30 is currently engaged in a call or, for any reason, the subscriber fails to answer. This feature sends a Transfer To Number Request Message to HLR 24 requesting further routing instructions. Because HLR 24 is unable to distinguish between calls originating from MSC 20 and calls originating from IP 22, however, all calls will be forwarded to the subscriber's voice mail system.
As readily seen, forwarding a wireless call to a voice mail system in the case of single number service applications is undesirable, unnecessary, and wasteful of network resources.
Consequently, a need has developed for a method and system for conditionally forwarding calls to a wireless subscriber to an alternative device or system such as a voice mail system upon detection of a busy or no answer condition.